By Dean L. Courtney, Donald G. Mortensen, Joseph A. Orsi, Kristen M. Munk
Fisheries Research, Volume 46, Issues 1-3, May 2000, Pages 267-278, ISSN 0165-7836, DOI: 10.1016/S0165-7836(00)00151-X.

First ocean-year juvenile Pacific salmon (Oncorhynchus spp.) in the marine waters of southeastern Alaska were examined for origin identification in the summers of 1993-1997. Over 31,000 juvenile pink (O. gorbuscha), chum (O. keta), sockeye (O. nerka), coho (O. kisutch), and chinook (O. tshawytscha) salmon were scanned electronically for coded wire tags (cwt's). Cwt's were decoded to indicate tagging origins and release sites. Few (49) fish examined contained cwt's. A sub-sample of the scanned juvenile pink (1,698), chum (1,685), and sockeye (189) salmon were also examined for thermally induced otolith marks (thermal marks). Sagittal otoliths were processed, and thermal mark code patterns were resolved to identify marking facilities and release sites. Many of the pink (45), chum (483), and sockeye (12) salmon examined contained thermal marks. Most recovered cwt's and thermal marks originated in southeastern Alaska. Most thermally marked juveniles had migrated 100-150 km in 60-90 days from release locations in northern and central southeastern Alaska and were recaptured along a primary migration corridor in northern southeastern Alaska. The high proportion (15.1%) of otolith thermal mark recoveries has broad implications for the study of Pacific salmon life histories. In particular, systematic sampling for thermal marks may provide stock-specific insight into the early marine life histories of Pacific salmon species, especially pink and chum salmon, which otherwise are underrepresented in cwt recoveries.
Keywords: Otolith; Thermal mark; Pacific salmon; Stock origin identification; Coded wire tag

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